Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Rich annotations (readOnlyHint, idempotentHint, openWorldHint, destructiveHint=false) already establish this as a safe, side-effect-free read. The description adds only billing context ('usage-based billing; default estimate $0.012 USD, not a fixed price'), which is genuinely useful but is injected boilerplate rather than tool-specific behavior. No return-shape or pagination notes, though an output schema exists.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The core is a single front-loaded sentence with no wasted words. The appended pricing block is somewhat verbose and not relevant to invocation, slightly diluting conciseness.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present and annotations covering the safety profile, the description needn't explain return values. It states exactly what the endpoint yields, which is sufficient for a parameterless reference-list call; only explicit sibling routing is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so per the baseline a 4 applies. There is nothing for the description to compensate for, and schema coverage is nominally 100%.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'receive the list of Apple languages supported in App Data API.' The 'Apple' qualifier lets an agent distinguish it from the sibling get_dataforseo_app_google_languages without opening either schema, though it never names that sibling explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no guidance on when to call this versus the many sibling reference/list endpoints (google_languages, apple_locations, apple_categories). The purpose implies usage but nothing states prerequsites, sequencing, or when-not-to-use.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.